1. Field of the Invention
The present invention relates to a horizontal multijoint type robot having a greatly enlarged region within which the robot is able to operate.
2. Related Art
The horizontal multijoint type robot also called as scalar type robot usually includes a first arm and a second arm pivotally movable in horizontal planes through a first and a second joint shaft, respectively, a working shaft equipped on the distal end of the second arm and rotatable and movable up and down, and a handling device or the like mounted on the working shaft for carrying out desired working such as assembling, transferring or the like (refer to, for example, Japanese Patent Application Laid Open No. 84,688/1993).
A horizontal multijoint type robot of the prior art, however, includes a second arm which could not rotate more than 360 degrees owing to its structural limitation so that its operating area is of substantially a doughnut shape thus attended by the following problems.
(1) There are areas within which the robot could not be operated unless only a single arm is operated so that moving paths between two points would become lengthy, taking much time.
(2) As the region (working range) in which the robot is operated is narrower, there are many limitations in a limited space so that it would be very difficult to determine a layout for effectively arranging positions (in shortest distances) where the robot operates.
(3) If a wider operating range is attempted, the size of a robot would have to be enlarged in proportion to the working area, causing a problem of space.